Such a kind of technique is disclosed in Patent Reference-1, for example. Patent Reference-1 discloses a display device (hereinafter referred to as “view-dependent display device”) capable of displaying an image existing only in the gaze direction of the user by setting the focus point of light for displaying the image to around the center of the eyeball. By setting the light focus point to around the center of the eyeball, a view-dependent display device can let the light beam only in the gaze direction pass through the pupil thereby to let the user see an image only existing in the gaze direction.
Patent Reference-1: Japanese Patent Application Laid-open under No. 2002-90688